Abdominal Aortic Aneurysm



If someone presents with signs and symptoms of renal colic above the age of 40 without previous history of renal stones they have an AAA until proven otherwise


Presents as a triad of:

Abdominal or Back Pain of sudden onset

Collapse or Light-headedness

Hypotension

  • An abnormal blood-filled dilatation of a blood vessel (esp. in an artery resulting from disease of the vessel wall).
  • An abdominal catastrophe ( 30% misdiagnosed initially)
  • Abdominal aorta begins at the level of the aortic hiatus of the diaphragm at T12
  • Surface anatomy = Xiphoid sternum (dilated aorta palpable above the umbilicus)
  • The dilatation is part of a atherosclerotic process
  • An aneurysm is defined as a focal increase in the diameter (normal 2cm) of a vessel to greater than 50% of normal; anything less is considered arteriomegaly

Risk factors

  • Male
  • Age (biological age)
  • Smoking
  • Hypertension
  • FHx
  • Hypercholesterolaemia
  • Peripheral Vascular Disease
  • Diabetes in protective against AAA

Presentation

Sudden Pain

  • Back / Abdomen / Flank
  • Inguinal / Testicular

Collapse (Light-headedness)

Aortocaval fistula

  • High output cardiac failure
  • Pulmonary oedema (flash)
  • Leg congestion and swelling

Examination

  • Unwell
  • Hypotensive
  • Diaphoretic
  • SOB
  • Abdo. mass (pulsatile & expansile)

Initial Mx

  • Surgical On-Call when Dx suspected
  • Aim for Stable hypotension in resusc

Investigations:

  • Group Xmatch x6
  • FBC, U&E, Creat, Coag
  • ECG (Hardman Criteria)/AMI
  • Urinalysis - UOB negative
  • U/S Aorta (bedside)
  • CT Abdomen - if stable

Differential Diagnosis:


Surgical Prognosis Determined by:

Hardman Criteria:

Age > 76

+3 = 100% Mortality

+2 = 72% Mortality

+1 = 37% Mortality

Hb <9.0 g/dl
Creat >190mmol/l
Hx of LOC
Ischaemia on ECG

Additional Management:

Urinalysis - Qualitative Microscopic Haematuria

Urinary Catheter - Monitor Urinary Output

ABG - Acid/Base Status, Lactic Acid (bowel?)

Erect CXR - Free Air?

AXR not useful but may show loss psoas shadow

  • Approximately 90% (of AAA) are infrarenal
  • The average increase is 2 mm/yr diameter
  • Usually not repaired until they exceed 4-5 cm
  • Risk of rupture within 5 years is 25% at 5 cm diameter
  • AAA > 5 cm have a 3% risk of rupture over 10 years

References :

Medline Plus Online Medical Dictionary

Shein, M. and Rogers P. Schein’s Common Sense Emergency Abdominal Surgery 2nd Ed. Springer New York : 2005

Cameron, J Ed. Current Surgical Therapy 8th Ed. Elsevier/Mosby Philadelphia PA : 2001


Content by Dr Trajan Cuellar 30/09/2008. Last review Dr ÍOS 1/06/21.